Plus-Alias Detection

Some temp-mail services distribute plus-aliases on Gmail, Outlook, Hotmail, Live, MSN, and iCloud mailboxes. A domain check alone cannot distinguish those addresses from other users at the same provider.

Canonicalization

For supported providers, DISIFY compares a canonical form of the address with known temp-mail base accounts:

• Lowercase the local-part and domain.
• Strip everything from + to @ (the plus-alias tag).
• Map googlemail.com → gmail.com.
• For gmail.com only: remove dots from the local-part.
• Preserve dots for Microsoft and Apple domains.

An exact match sets disposable: true. Send the original address to the API; this normalization happens inside DISIFY, and the original alias pattern is also used for heuristics.

Flagged response

{
  "format": true,
  "alias": true,
  "domain": "gmail.com",
  "disposable": true,
  "dns": true,
  "whitelist": true,
  "confidence": 100,
  "signals": ["alias_base_exact"],
  "domain_info": { "tld": "com", "is_subdomain": false, "parent_domain": null },
  "mx_info": [
    "gmail-smtp-in.l.google.com",
    "alt1.gmail-smtp-in.l.google.com",
    "alt2.gmail-smtp-in.l.google.com",
    "alt3.gmail-smtp-in.l.google.com",
    "alt4.gmail-smtp-in.l.google.com"
  ],
  "role": false,
  "free": true
}

alias is true here because the address carries a +tag; it flags the presence of an alias tag, not the verdict itself.

whitelist + disposable together

Because an exact base-account match overrides the domain-level whitelist, you'll occasionally see "whitelist": true alongside "disposable": true. The whitelist applies to the base domain; the alias override applies to the specific address. Trust disposable as the final verdict.

Heuristic patterns

The free_provider_alias_pattern signal reports suspicious patterns without an exact base-account match:

• Gmail — a base local-part with 4+ dots or 2+ numeric dot segments.
• Any supported provider — a short alphanumeric +tag containing both letters and digits.

It adds 35 confidence points without changing disposable itself. A suspicious pattern is not proof of a temp-mail account. See Confidence Scoring.

Why it matters for caching

[email protected] and [email protected] can have different verdicts. A cached domain-level verdict must not replace either individual check. If you cache individual results, keep the complete input and requested features separate, and use an explicit freshness policy. See Best Practices.